import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
//import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws IOException {
//        Scanner sc = new Scanner(System.in);
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        ArrayList<String> list = new ArrayList<>();
//        String[] s = sc.nextLine().split(" ");
        String[] s =bf.readLine().split(" ");

        int flag = 1;
        for (int i = 0; i < s.length; i++) {
            if (list.contains(s[i])) {
                System.out.println("yes");
                flag = 0;
                break;
            }
            list.add(s[i]);
        }
        if (flag == 1)
            System.out.println("no");
    }
}
